This disclosure relates to storing information in a memory. Some memories include storage cells that transit asymmetrically among states. For example, flash memories may store information in the states of floating-gate cells. The state of a floating-gate cell may depend on the amount of charge trapped in the cell, and writing information to a flash memory may include injecting charge into one or more of the floating-gate cells (e.g. by the hot-electron injection mechanism or the Fowler-Nordheim tunneling mechanism). Rewriting information to the flash memory may include erasing all of the information stored in a collection (e.g. a block) of floating-gate cells.